Procedure and device for the production of a plasma

ABSTRACT

The present invention concerns a procedure for the production of a plasma that is at least co-produced in the vacuum chamber ( 1   a ) of a vacuum recipient ( 1 ) of a device suitable for plasma processing with at least one induction coil ( 2 ) carrying an alternating current, where the gas used to produce the plasma is fed into the vacuum chamber ( 1   a ) through at least one inlet ( 3 ) and the vacuum chamber ( 1   a ) is subject to the pumping action of at least one pump arrangement ( 4 ), and where a possibly pulsed direct current is also applied to the induction coil ( 2 ) in order to influence the plasma density.

AREA OF THE INVENTION

The present invention concerns a procedure for the production of aplasma produced by means of an induction coil in the vacuum chamber of avacuum recipient, as well as a device suitable for carrying out theprocedure in accordance with the invention. The invention furtherconcerns the use of the procedure in accordance with the invention forproviding a substrate with a possibly reactive coating or performing apossibly reactive etching on such a substrate.

BACKGROUND OF THE INVENTION

When substrates are reactively processed in a vacuum, as is the case—forexample—in semiconductor production, it is customary to employ a plasmaproduced in the vacuum chamber of a vacuum recipient for a multitude ofprocess steps, cases in point being the possibly reactive coating or thepossibly reactive etching of a substrate.

In this connection it is known that the plasma can be produced byinductive and/or capacitative means.

EP 0 271 341 A1, for example, describes a device for the dry etching ofsemiconductor disks that comprises an induction coil for plasmaproduction and an electrode device for extracting ionized particles fromthe plasma onto the substrate. In the device described in U.S. Pat. No.6,068,784, again, energy for plasma production is inductively coupledinto the vacuum chamber of the vacuum recipient by means of a coil-typeantenna, the vacuum chamber in this case serving as reactor. Thesubstrate is situated on an electrode that serves as substrate carrierand to which there is applied a so-called RF (radio frequency) bias orpolarizing potential.

U.S. Pat. No. 5,460,707 describes a device for capacitative plasmaproduction that can also be used for coating purposes. A magneticfield—produced by an additional permanent or electromagnet—may beprovided in this case for controlling the plasma density distribution orproducing a locally greater plasma density.

When substrates are subjected to vacuum processing, as is the case—forexample—in semiconductor production, it is very important to have anextremely uniform plasma density distribution over the entire surface ofthe substrate in order to assure an appropriately uniform substrateprocessing. To this end it is essential to screen or compensate alldisturbing external influences, especially external fields.

Although, for example, it is theoretically possible to use aferromagnetic shell to screen the vacuum recipient, this is ratherdisadvantageous from a practical point of view, because such a shellwould considerably increase the weight of the vacuum recipient.Furthermore, it would become more difficult to gain access to the vacuumrecipient whenever maintenance or repair work has to be carried out.

EP 0 413 283 teaches that a planar plasma can be obtained by means of anelectrically conductive planar pancake coil, the induction field beingproduced by connecting a high-frequency voltage source to the pancakecoil and coupled in through a dielectric screening.

U.S. Pat. No. 6,022,460 suggests that a further magnetic field—producedby a pair of Helmholtz coils—should be allowed to act on the plasma,which can be inductively produced (or at least co-produced), forexample, by means of either a pancake coil to which there is applied ahigh-frequency alternating voltage or a coil in the form of a vacuumbell. Applied to the pair of Helmholtz coils is a direct and alternatingcurrent combination such as to produce a weak magnetic field that ismodulated by the alternating current component, said modulation beingdescribed as a “shaking” of the magnetic field”. According to the patentin question, this serves essentially to obtain an increase of the plasmadensity and an improvement of the uniformity of the plasma.

One drawback of the device for the production of a plasma described inU.S. Pat. No. 6,022,460 consists of the fact that the additional pair ofHelmholtz coils makes it more difficult to obtain a compact design andalso increases the cost of the device. Since considerations ofhigh-frequency technology require the induction coil to be decoupledfrom the pair of Helmholtz coils, it is absolutely essential that theinduction coil should be spatially separated from the Helmholtz coils.

The present invention therefore sets out to make available a procedureand a device for the production of a high-density plasma that wouldeither avoid the described drawbacks associated with the state of theart or be affected by them only to a lesser extent. Further tasks of thepresent invention will be brought out by the detailed descriptionthereof given hereinbelow.

BRIEF DESCRIPTION OF THE INVENTION

The present invention concerns a procedure for the production of aplasma that is at least co-produced in the vacuum chamber (1 a) of avacuum recipient (1) by means of at least one induction coil (2)carrying an alternating current, where the gas used to produce theplasma is allowed to enter the vacuum chamber (1) through at least oneinlet (3) and the vacuum chamber (1 a) is subject to the pumping actionof at least one pump arrangement (4) and where—for the purposes ofinfluencing the density of the plasma—a possibly modulated andpreferably pulsed direct current is passed through the induction coil(2).

The present invention further concerns the use of the procedure inaccordance with the invention for the possibly reactive coating and orthe possibly reactive etching of substrates (9).

The invention further concerns a device suitable for plasma processingthat comprises at least one induction coil (2) for at least co-producingthe plasma in the vacuum chamber (1 a) of a vacuum recipient (1), wherethe vacuum chamber (1 a) is provided with at least one inlet (3) foradmitting the gas serving for the production of the plasma and a pumparrangement (4), and where the induction coil (2) is connected to one ormore voltage generators that supply the induction coil with analternating current and a direct current, the latter possibly pulsed ina unipolar or a bipolar manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of a device in accordance withthe invention suitable for plasma processing.

FIG. 2 shows the normalized etching depth along a diagonal of a siliconwafer, where the plasma used for the etching was at least co-produced byan induction coil carrying either a direct and an alternating current(Curve I) or merely an alternating current (Curve II).

DETAILED DESCRIPTION OF THE INVENTION

The device in accordance with the invention suitable for plasmaproduction comprises a vacuum recipient 1 with a vacuum chamber 1 a thatcan be evacuated by means of one or more pump arrangements 4.

In a preferred embodiment the vacuum recipient 1 comprises an outercasing 20 made of such metals as, for example, stainless steel oraluminium in order to assure good sealing of the vacuum recipient and toscreen it, especially against stray external fields On the vacuum sidethe metal casing 10 of the vacuum recipient 1 may preferably be providedwith a dielectric inner casing 7 that could be, for example, eitherself-supporting or applied as a coating to the inside of the outercasing 10. The dielectric material is preferably chosen in such a way asto be not only as inert as possible with respect to the gases used forreactive coating and etching processes, gases that may contain suchelements as chlorine and fluorine, but also as permeable as possible asfar as the coupled power is concerned. Preferred dielectric materialscomprise, among others, polymeric materials, especially ceramicmaterials, quartz and aluminium oxide. But it is also possible, forexample, for only the side wall of the vacuum recipient 1 to be eitherwholly or partly lined or coated with dielectric material or to be madeof a dielectric material, while both the upper and the lower faces areprovided with metallic connections (couplings) as described in WO00/19,483. The vacuum recipient 1 described in EP 0 413 283 is providedwith a dielectric screening that may be contained, for example, in theupper cover wall of the vacuum recipient 1.

The above description of the vacuum recipient 1 is to be understood as amere example and is intended to explain the invention, but not to limitit.

The vacuum chamber 1 a contains one or more gas inlets 3 that serve toadmit the gas used for the production of the plasma. The gas, which mayconsists of a single gaseous compound or also of a mixture of severalgaseous compounds, is chosen by taking due account of the chemicalcomposition and the physical parameters of the substrate 9 that is to beprocessed and the modification of the substrate surface that is to beobtained. If the surface of the substrate is to be cleaned (sputteretching), the gas may contain, for example, argon or some other inertgas, while the gases used for reactive etching processes may contain,for example, chlorine (Cl₂), silicon tetrachloride (SiCl₄), borontrichloride (BCl₃), carbon tetra-fluoride (CF₄), trifluoromethane(CHF₃), sulphur hexafluoride (SF₆) and/or oxygen (O₂). When substrateshave to be coated with thin films (for example, by means of chemicalvapour deposition—CVD or plasma enhanced chemical vapourdeposition—PECVD), it is possible to use organometallic compounds,methane (CH₄), silicon hydride (SiH₄), ammonia (NH₃), nitrogen (N₂) orhydrogen (H₂). The aforementioned gaseous compounds and processes forthe processing of substrates 9 are once again to be understood asexamples and intended solely to explain the invention, not to limit it.

The flow of the gases and the power of the pumping arrangement(s) 4 arepreferably chosen in such a manner as to make the pressure in the vacuumchamber 1 a of the vacuum recipient 1 come to lie especially between0.01 and 10 Pa and preferably between 0.05 and 0.02 Pa.

The device in accordance with the invention contains at least oneinduction coil 2 by means of which the plasma produced in the vacuumchamber 1 a of the vacuum recipient 1 is at least co-produced. Theinduction coil(s) 2 is/are preferable arranged in the vacuum recipient 1and/or the vacuum chamber 1 a in such a manner as not to be exposed tothe plasma, thereby avoiding, for example, the deposition ofelectrically conducting interference coatings or other coatings on theinduction coil(s) 2 or damage of the induction coil(s) 2 caused by theplasma. The induction coil(s) 2 is/are preferably separated by means ofdielectric screening (for example: a dielectric inner casing 7) from atleast the part of the vacuum chamber 1 a in which the plasma isproduced. The induction coil(s) 2 may preferably be arranged alsooutside the vacuum chamber 1 a.

The device in accordance with the invention contains one or moreinduction coils 2, preferably one or two induction coils 2, andespecially one induction coil 2.

The form of the induction coil(s) 2 may vary and is preferably chosen insuch a manner that as uniform as possible an induction field is obtainedeven without causing a direct current to pass through the inductioncoil(s) 2.

In a preferred embodiment of an induction coil 2 said coil compriseswindings that are wound directly on the vacuum chamber 1 a and/orpreferably on a dielectric internal casing 7 situated inside thechamber. In the device in accordance with the invention that isschematically illustrated by FIG. 1 the coil windings are wound, forexample, on the side walls of the dielectric internal casing 7. In thiscase the uniformity of the induction field can be influenced, forexample, by the number and the arrangement of the windings of theinduction coil(s) 2 and the geometric dimensions of the dielectricinternal casing 7.

In another embodiment the induction coil 2 assumes the form of a flat(pancake) or planar coil that may consist, for example, of a number ofspiral-shaped windings or a series of windings arranged in concentriccircles, as described in EP 0 413 282. The flat coil could, for example,have a preferably circular or ellipsoidal form. The concept “flat” or“planar” means that the ratio between the thickness of the coil and theextent of the coil in the two other directions at right angles to thethickness is smaller than 0.3 and, preferably, smaller than 0.2. EP 0413 282 discloses that the pancake coils are preferably arranged closeto a dielectric screening in the outer casing 10 of the vacuumrecipient, said screen acting as a dielectric window and permitting thecoupling of the induction field. It is, of course, also possible toarrange the flat coil close to the dielectric inner casing 7.

In another preferred embodiment the induction coil 2 has the form of avacuum bell as disclosed in U.S. Pat. No. 6,022,460.

It has been found that the density of the plasma at least co-produced bymans of the induction coil(s) 2 can be influenced and that, inparticular, the uniformity of the plasma can be increased when to theinduction coil(s) 2 there is applied not only an alternating current,but also and at the same time a direct current.

The application to the induction coil(s) 2 of an alternating currentserves to couple the high-frequency power into the vacuum recipient forat least the co-production of the plasma. For this purpose the inductioncoil 2 is connected to a high-frequency voltage generator 6, preferablythrough an adapter network 13. The adapter network 13 serves to adaptthe original resistance of the high-frequency voltage generator 6 andthe impedance of the induction coil(s) 2 and the vacuum chamber 1 aand/or the plasma produced therein, thus making it possible to obtain ahighly effective coupling of the high-frequency power.

In connection with the present invention the concept of “high frequency”is used for electromagnetic vibrations or waves having a frequencybetween 10 kHz and 3 GHz. The high-frequency voltage generator 6 maywork in a broad high-frequency spectrum from preferably 100 kHz to 100MHz, more preferably between 100 kHz and 14 MHz and even more preferablybetween 400 kHz and 2 kHz.

The choice of a preferred frequency also depends on the geometry of theinduction coil(s) 2. Thus, in the case of non-flat, three-dimensionalinduction coil(s) 2, as might be obtained, for example, when the coilwindings are wound round the dielectric inner casing 7 and in which thehigh frequency energy is coupled into the vacuum chamber 1 a via thevolume of the space within the winding, the chosen frequency willpreferably lie between 100 kHz and 2 MHz and especially between 200 kHzand 1 MHz. In the case of two-dimensional pancake coils, on the otherhand, where the high-frequency energy is coupled into the vacuum chamber1 a via the area of the coil, the chosen frequencies will be ratherhigher, preferably between 2 MHz and 14 MHz. The preferred upperlimiting value of this frequency range is due to the fact that thestandard frequency of the high-frequency voltage generators most widelyused in industry is 13.56 MHz. This frequency is approved for industrialuse by international telecommunication agreements.

It has been found that the density distribution of the plasma can beinfluenced when a direct current is additionally applied to theinduction coil(s) 2 and that, preferably, the uniformity of the plasmacan be thereby improved, for example, over the surface of a substrate 9.To this end the induction coil 2 is also connected to a direct voltagegenerator 6′, preferably through a low-pass filter 12. The low-passfilter 12, which may comprise, for example, a coil and a capacitorconnected in parallel with it, is preferably designed in such a mannerthat the direct current can reach the induction coil 2 while thehigh-frequency current is blocked, so that the latter cannot find itsway into the direct current source.

The direct current may be either uniform or modulated, for example, itmay be pulsed in a unipolar or a bipolar manner. Bearing in mind thenumber of windings of the induction coil 2, the direct current will beset in such a manner that the product of the number of windings and thedirect current will amount both on average and as an absolute value tobetween 10 and 1000 and preferably between 100 and 400 ampere windings.The number of windings of the induction coil 2 is preferably at least 7,but a minimum of 10 windings would be better and a minimum of 12 betterstill, since the current needed to render the density distribution ofplasma uniform will increase as the number of windings diminishes, sothat the demands made on the direct current generator 6′ and thelow-pass filter 12 will tend to become greater.

The plasma density distribution can be measured, for example, by using aLangmuir probe. Since in the case of sputter etching and reactiveetching process, and possibly also in the case reactive coatingprocesses, the uniformity of the plasma density distribution over thearea of the substrate 9 affects the uniformity of the etching depthdistribution and or the coating thickness distribution along, forexample, a section through the substrate, the uniformity of the plasmadensity distribution may also be measured by measuring the distributionof the etching depth and/or the coating thickness.

In the case of a thermally oxidized silicon wafer, for example, theetching depth can be determined by using, for example, an ellipsometerto measure the thickness of the silicon oxide layer prior to theetching, for example, in a raster covering the entire surface of thesilicon wafer or along a diameter of the silicon wafer. The thickness ofthe residual silicon oxide layer is then measured after the etchingprocess has been completed. The etching depth follows from thedifference between the thicknesses of the silicon layer before and afterthe etching process

This procedure can be applied in an analogous manner to measure coatingthicknesses.

The uniformity or evenness of the distribution of, for example, theetching depth, as also of the plasma density or the coating thickness,for example, along a section through the substrate 9 can becharacterized by the so-called uniformity index, which is defined as

Uniformity index=(Maximum value−Minimum value)/(Maximum value+Minimumvalue)

where the maximum value and the minimum value are, respectively, thelargest and the smallest value of the characterizing distribution on,say, the entire surface area of the substrate 9 or along a sectionthrough the substrate. The uniformity index is usually stated as apercentage.

The direct current applied to the induction coil 2 is preferably chosenin such a manner as to make the uniformity index of the plasma densitydistribution, etching depth or coating depth, for example, along anarbitrarily chosen section through the substrate 9 or, for example, overa particular part of or the entire surface of the substrate 9 amount tonot more than 10%, preferably not more than 7.5% and, even better, notmore than 5%.

In yet another preferred embodiment of the device in accordance with theinvention said device contains at least a pair of electrodes 5 a, 5 bseparated by a certain distance. In the particular design of a vacuumprocessing chamber described in WO 00/19,483 the electrodes 5 a, 5 b maybe formed, for example, by the metallic connections in the upper andlower cover wall of the vacuum recipient 1, these walls beinggalvanically separated from each other by the side walls made ofdielectric material. U.S. Pat. No. 6,068,784 describes an arrangement ofthree electrodes in which the substrate table 8 serves as cathode andthe side wall of the vacuum recipient as the anode, while the cover wallof the upper dome-shaped protuberance of the vacuum recipientconstitutes a third electrode.

In a specially preferred embodiment one electrode 5 a of the electrodepair 5 a, 5 b is formed by the substrate table 8 that the substrate 9bears against and/or to which it is attached by means of the normallyused electrostatic or mechanical holding and/or centering device (in thecase of a wafer substrate sometimes referred to as wafer chuck). Thesubstrate table itself will normally be electrically insulated from thecasing 10 of the vacuum chamber. The counter-electrode 5 b may beconstituted, for example, by an electric connection in the upper coverwall or the end face of the vacuum chamber when such a connection ispresent. In a specially preferred variant the possibly circularsubstrate table 8 is surrounded by a ring that serves ascounter-electrode and is usually described as dark space screening. Theinsulation between the substrate table 8 and the dark space screening inthe upper part of the dark space screening is provided by the vacuum inthe vacuum chamber 1 a. In its lower part the dark space screening isfixed to the substrate table 8—though galvanically separated from it—insuch a way as to be centered with respect to a ring-shaped ceramicinsulator.

The electrode pair 5 a, 5 b may be connected, for example, to a directvoltage source, possibly pulsed in a unipolar or a bipolar manner, analternating voltage source, or simultaneously to a direct and analternating voltage source. The plasma is capacitatively excited by thevoltage applied to the electrode pair 5 a, 5 b, which is also describedas bias.

Preferably applied to the electrode pair 5 a, 5 b is a direct voltage oran alternating voltage, especially a high-frequency alternating voltagehaving a frequency between 100 kHz and 100 MHz. When selecting asuitable frequency of the alternating voltage, due account is preferablytaken of the effects on the substrate 9 and/or the vacuum chamber 1 adescribed in U.S. Pat. No. 6,068,784, column 4, lines 23-52; specificreference is here made to this discussion. In a preferred embodiment ofthe present invention, in which the substrate table 8 is used aselectrode 5 a and a dark space screening is used as counter-electrode 5b, the substrate table 8 is connected to a high-frequency voltagegenerator 11 with a frequency of preferably more than 3 MHz and,specially preferred, more than 10 MHz, while the dark space screening isgrounded.

FIG. 1 shows a schematic section through a preferred embodiment of thedevice in accordance with the invention. The vacuum recipient 1comprises a tank 10—which is made of, for example, stainless alloy steeland is capable of being evacuated—encloses the vacuum chamber 1 a andcontains a dielectric inner casing 7 made of, for example, quartz oraluminium oxide. The induction coil 2 is wound around the dielectricinner casing and is connected to the alternating voltage generator 6through the adapter network 13 and also with the direct voltagegenerator 6′ through the low-pass filter 12; the circuit is completed bygrounding. The substrate table 8, which sustains the substrate 9 restingon it, serves as electrode 5 a and is surrounded by a circular darkspace screening, which is arranged in a centered position and acts ascounter-electrode 5 b. The vacuum chamber 1 a is subject to the pumpingaction of a pump arrangement 4. The upper cover wall of the vacuumrecipient 1 is provided with a gas inlet 3 situated at its centre.

In a concrete embodiment of the arrangement schematically illustrated byFIG. 1, which had been designed for processing a wafer having a diameterof 200 mm, the diameter of the dielectric inner casing amounted to 275mm. The distance between the substrate table 8 and the upper cover wallof the vacuum recipient 1 was 180 mm. The induction coil 2 wound aroundthe dielectric inner casing 7 had a diameter of 304 mm and consisted of15 windings. Argon for sputter etching was fed into the chamber throughthe gas inlet 3, so that an operating pressure of 10⁻³ was attained. Thebiasing voltage applied to the substrate table 8, which served aselectrode 5 a, had a frequency of 13.56 MHz, while the dark spacescreening that served as counter-electrode was grounded. The inductioncoil 2 was connected to an alternating voltage generator 6 operated at400 kHz through an adapter network 13 that consisted of two capacitors.The magnetic field induced by this arrangement in the inner space of theinduction coil 2 amounted to about 5 Gauss. The induction coil 2 wasalso connected to a direct voltage generator through a low-pass filter12 that consisted of a capacitor and a coil connected in parallel withit. The direct current, which was chosen in such a manner that thesputter etching depth distribution along a diameter of the wafer thatserved as substrate 9 had a uniformity index of less than ±3%, amountedto about 10 A and produced a magnetic field of about 12 Gauss.

FIG. 2 shows the normalized sputter etching depth distribution along adiameter of a circular silicon wafer having a diameter of 300 mm thathad previously been subjected to thermal oxidation. The measurementswere made under the operating conditions described in connection withFIG. 1 and in a similar device that had the geometric dimensions neededto accommodate a 300 mm wafer. Curve I shown in FIG. 2 was obtained fora procedure in accordance with the invention in which an alternatingcurrent and an additional direct current of about 10 A were applied tothe induction coil 2. For comparison purposes, Curve II shows thesputter etching depth distribution that is obtained when only analternating current is applied to the induction coil. It can be seenfrom Curve II that when only an alternating current is applied to theinduction coil, the sputter etching depth diminishes as the edge of thewafer substrate 9 is approached; furthermore, the sputter etching depthdistribution not symmetrical. Curve I shows that that the uniformity ofthe sputter etching depth distribution is clearly improved when anadditional direct current is applied to the induction coil 2. To allintents and purposes the sputter etching depth distribution is no longerassociated with any lack of symmetry. In particular, the reduction ofthe sputter etching depth towards the wafer edges observed in Curve IIis now compensated. The homogenization of the plasma densitydistribution attained by means of the additionally applied magneticfield produced by the direct current reflects in a uniformity index ofless than ±3%. If so desired, the amperage of the direct current canalso be chosen so as to obtain an overcompensation of Curve II andtherefore greater etching depths at the edges of the wafer than in thecentre; in that case the uncompensated Curve II, which has a convexcurvature, is in a certain sense “reversed” with respect to thecompensated state in accordance with Curve I, so as to produce anovercompensated curve with a concave curvature.

In a preferred embodiment of the invention as a processing station thedevice in accordance with the invention can be a component of aso-called cluster. The term cluster is here understood as referring to acombination of several and often different processing stations that areserved by a common transport device, a handling robot for example. A PVD(physical vapour deposition) plant might here be named as an example ofa further processing station. The various processing stations arepreferably separated from the transport space by means of appropriatesluicegates.

In such a cluster the transport device will be used to introduce thesubstrate 9 through a transfer sluicegate (not shown in FIG. 1) into thedevice in accordance with the invention The transport device depositsthe substrate 9 on the substrate table 8, where it will be centered (ifnecessary) and appropriately retained. Following vacuum-tight closure ofthe sluicegate, the vacuum chamber is evacuated by means of the pumpingarrangement 4; in parallel therewith or immediately afterwards thesubstrate 9 is brought to the desired processing temperature, possiblyby means of tempering devices contained in the substrate table 8. Thegas needed to produce the plasma is then fed into the chamber throughthe gas inlet 3. Thereafter the plasma is ignited by applying thehigh-frequency voltage to the induction coil 2 and the high-frequencybias to the substrate table 8. In parallel therewith the direct currentis applied to the induction coil 2. Following completion of the desiredprocessing, the substrate 9 is removed from the vacuum recipient 1through the sluicegate.

1-25. (canceled) 26: A device for the production of a plasma thatcomprises at least one induction coil (2) for at least co-producing theplasma in a vacuum chamber (1 a) of a vacuum recipient (1), where thevacuum chamber (1 a) is provided with at least one inlet (3) to admit agas serving for the production of the plasma, with at least one pumparrangement (4), a substrate table (8) and a dark space screening, andcharacterized in that the induction coil (2) is connected to analternating current and a direct current, and wherein the direct currentis continuously applied during the plasma processing simultaneously withsaid alternating current to the induction coil (2) in order to influencethe plasma density, said induction coil (2) is separated by means of adielectric inner casing (7) or a dielectric window from at least thepart of the vacuum recipient (1 a) in which the plasma is produced, thealternating current is produced by a high frequency generator (6)operating at a frequency between 100 and 14,000 kHz, the substrate table(8) is provided for a substrate (9), the substrate table (8) is formedby an electrode (5 a), the dark space screening is used as acounter-electrode (5 b), and the plasma is co-produced or co-exited byan electric voltage applied to at least one pair of electrodes (5 a), (5b) separated by a certain distance and said pair of electrodes comprisessaid substrate table (8) and said dark space screening. 27: The devicein accordance with claim 26, wherein the induction coil (2) is connectedto an alternating voltage generator (6) through an adapter filter (12)and to a direct voltage generator (6′) through a low-pass filter (13).28: A cluster containing several processing stations that are connectedby means of transfer sluicegates to a common transport device andwherein at least one processing station is a device in accordance withclaim
 26. 29: A cluster containing several processing stations that areconnected by means of transfer sluicegates to a common transport deviceand wherein at least one processing station is a device in accordancewith claim
 27. 30: The apparatus according to claim 26, wherein theelectric voltage is an alternating voltage having a frequency of atleast 1 MHz. 31: The apparatus according to claim 26, wherein theelectric voltage is a direct voltage pulsed in a unipolar or bipolarmanner. 32: The apparatus for the production of a plasma according toclaim 26, wherein the gas is selected from the group consisting ofargon, inert gases, chlorine, silicone tetrachloride, boron dichloride,carbon-tetra fluoride, tri-fluoride methane, sulfur hexafluoride,oxygen, methane, silicon hydride, ammonia, nitrogen and hydrogen. 33:The apparatus for the production of a plasma according to claim 26,wherein the induction coil is of a form selected from the groupconsisting of flat, pancake and plainer coils.